This example lacks certain features to make it work reliably l, but it shows basically how a class H amp should behave. The supply rail is being modulated by the same signal that appears on the output, and follows the curvatures of the wave, just a few volts above it. This way if the output stage is in class A amp, the average power consumption will always be the same, and the efficiency wouldn't worsen with lower output levels. You still benefit from the increased linearity of the amp, but also benefit from increased efficiency, if the supply rail modulator is made from a more efficient class of amplifier (Class B or maybe even D, although I haven't encountered such a revision of this type of amps).
